(1) can a single wire, e.g. copper wire, support full duplex transmission?

(2) still a single single wire, can it support transmission of multiple bits at a time in one direction?

(3) USB supports serial transmission, theoretically a single wire is enough. But why it has so many wires? ---I am not an electrical engineer, this question might sound too simple.

  • "I am not an electrical engineer" This question is really more on-topic for our sister site, Electrical Engineering.
    – Ron Maupin
    Apr 28, 2023 at 13:11

1 Answer 1


A 'single wire' as such isn't possible. At the very least, you require a signal wire plus a ground connection for single-ended signaling, or a twisted pair for differential signaling. Fiber can use a single strand, of course. And there's wireless.

  1. yes, using either echo cancellation (e.g. 1000BASE-T), frequency-division duplex (e.g. xDSL) or (for fiber) wavelength-division duplex (e.g. 1000BASE-BX10)
  2. yes, using MLT, PAM or a more complex multi-bit modulation (esp. QPSK or QAM)
  3. copper very often uses differential signaling over twisted pairs for cost reasons, USB is off topic here though

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.